[CRIU] [PATCH 2/2] inet: set IP_FREEBIND before binding socket to an ipv6 address

[Andrew Vagin]

On Thu, Nov 19, 2015 at 04:52:40PM +0300, Pavel Emelyanov wrote:
> On 11/19/2015 03:38 PM, Andrew Vagin wrote:
> > On Thu, Nov 19, 2015 at 03:33:37PM +0300, Pavel Emelyanov wrote:
> >> On 11/18/2015 06:58 PM, Andrey Vagin wrote:
> >>> From: Andrew Vagin <avagin at virtuozzo.com>
> >>>
> >>> When we restore ipv6 addresses, they go through a “tentative” phase
> >>> and sockets could not be bound to them in this moment.
> >>>
> >>> Reported-by: Ross Boucher <boucher at gmail.com>
> >>> Signed-off-by: Andrew Vagin <avagin at virtuozzo.com>
> >>> ---
> >>>  sk-inet.c | 29 ++++++++++++++++++++++++-----
> >>>  1 file changed, 24 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/sk-inet.c b/sk-inet.c
> >>> index 779a1bd..a973000 100644
> >>> --- a/sk-inet.c
> >>> +++ b/sk-inet.c
> >>> @@ -633,17 +633,29 @@ static int restore_sockaddr(union sockaddr_inet *sa,
> >>>  
> >>>  int inet_bind(int sk, struct inet_sk_info *ii)
> >>>  {
> >>> +	bool rst_freebind = false;
> >>>  	union sockaddr_inet addr;
> >>>  	int addr_size;
> >>> -	int val;
> >>>  
> >>>  	addr_size = restore_sockaddr(&addr, ii->ie->family,
> >>>  			ii->ie->src_port, ii->ie->src_addr);
> >>>  
> >>> -	val = 1;
> >>> -	if (setsockopt(sk, SOL_IP, IP_FREEBIND, &val, sizeof(int))) {
> >>> -		pr_perror("Unable to set IP_FREEBIND");
> >>> -		return -1;
> >>> +	/*
> >>> +	 * ipv6 addresses go through a “tentative” phase and
> >>> +	 * sockets could not be bound to them in this moment
> >>> +	 * without setting IP_FREEBIND.
> >>> +	 */
> >>> +	if (ii->ie->family == AF_INET6) {
> >>> +		int yes = 1;
> >>> +
> >>> +		if (restore_opt(sk, SOL_IP, IP_FREEBIND, &yes))
> >>> +			return -1;
> >>> +
> >>> +		if (ii->ie->ip_opts && ii->ie->ip_opts->freebind)
> >>> +			/* don't restore freebind in restore_ip_opts() */
> >>
> >> At all? When will it get restored then?
> > 
> > We set the right value here, 
> 
> Where? If we're in this if branch then rst_freebin is false and we
> don't even call restore_opt() below.

we set freebind and ii->ie->ip_opts->freebind is true.

restore_ip_opts() is called for each ip socket

> 
> > so we don't need to restore it in restore_ip_opts()
> >>
> >>> +			ii->ie->ip_opts->has_freebind = false;
> >>> +		else
> >>> +			rst_freebind = true;
> >>>  	}
> >>>  
> >>>  	if (bind(sk, (struct sockaddr *)&addr, addr_size) == -1) {
> >>> @@ -651,6 +663,13 @@ int inet_bind(int sk, struct inet_sk_info *ii)
> >>>  		return -1;
> >>>  	}
> >>>  
> >>> +	if (rst_freebind) {
> >>> +		int no = 0;
> >>> +
> >>> +		if (restore_opt(sk, SOL_IP, IP_FREEBIND, &no))
> >>> +			return -1;
> >>
> >> Why here? Why not delay "NO" till actual options restore?
> > 
> > because we restore only "yes", "no" is default.
> 
> Yes, "no" is the default and you just set "no" _again_ here. Why?

because we set true and set rst_freebind to return it back
> 
> >>
> >>> +	}
> >>> +
> >>>  	return 0;
> >>>  }
> >>>  
> >>>
> >>
> > .
> > 
>